Inlet nozzle for a degassing vessel for metallurgical melting operating according to the rh method

ABSTRACT

An inlet snorkel for a degassing vessel operating by the RH process. The inlet snorkel is for a degassing vessel for metallurgical melting using the RH process. Gas injection pipes through which inert gas can be introduced into the inlet snorkel are distributed along the axial length of the inlet snorkel, and groove-like guide shapes are provided upstream of these gas injection pipes so as to project into the clear cross section of the inlet snorkel.

PRIORITY CLAIM

This is a U.S. national stage of Application No. PCT/DE2009/001096, filed on Aug. 3, 2009, which claims priority to German Application No: 10 2008 037 166.1, filed: Aug. 7, 2008, the contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention is directed to an inlet snorkel for a degassing vessel for metallurgical melting using a Ruhrstahl-Heraeus (RH) process.

2. Related Art

In the RH process, molten steel is conveyed from a ladle in an up leg by a delivery gas, particularly argon, which is fed into the up leg above the liquid steel level, into an evacuation vessel due to the expansion in volume of the delivery gas in the up leg and a pressure difference between outside air pressure and negative pressure in the evacuation vessel. Argon bubbles present nuclei for CO formation and promote deoxidation and removal of nonmetal particles. The steel drawn into the evacuation vessel is atomized resulting in an increased surface and, therefore, good degassing.

It is known from EP 297 850 A1 to arrange a plurality of conduits around the circumference of an inlet snorkel so as to be divided into two groups, with gas under high pressure being admitted to one group and gas under low pressure to another group. In this way, the supplied gas flows penetrate to different depths in the molten metal guided through the snorkel and allow a uniform gassing of the molten metal over the cross section of the snorkel.

It is known from the literature to influence flow through a magnetic field: “Modeling of Two-Phase in RH Vacuum Degassing Vessel with the Effect of the Rotation Magnetic Field”, AISTech 2004 Proceedings, Volume 1, pp. 1125-1133, Baokuan Li et al. (PRC). This solution for exerting a magnetohydrodynamic effect on the melt flow provides a water-cooled component below a floor of an RH vessel. This construction is too large for technical application. Further, the water cooling presents a safety hazard.

SUMMARY OF THE INVENTION

It is the object of the invention to improve the flow conditions within the inlet snorkel.

According to one embodiment of the invention, an inlet snorkel for a degassing vessel for metallurgical melting using the RH process is characterized in that gas injection pipes through which inert gas can be introduced into the inlet snorkel are distributed along the axial length of the inlet snorkel, and in that groove-like guide shapes are provided upstream of these gas injection pipes so as to project into the clear cross section of the inlet snorkel.

Accordingly, in one embodiment of the invention, a passive flow guidance in the inlet snorkel of the RH installation is realized.

In one embodiment of the invention, the melt rising in the inlet snorkel of a RH installation and the emulsified inert gas bubbles are homogenized through a passive flow guidance.

In passive influencing of flow, as distinct from active influencing of flow (e.g., bubbling in of gas), the primary fluid is influenced exclusively by formative steps.

This goal is achieved by a special shaping of the refractory lining in axial direction of the inlet snorkel. The lining proceeds from the inlet side, i.e., from bottom to top, through a plurality of groove-like guide shapes which are twisted by a determined angle and project into the melt. These guide shapes extend into the inlet snorkel and induce a swirling in the rising multiphase mixture of melt and gas bubbles.

As a result, the gas bubbles are transported away from the refractory wall in direction of the axis of the inlet snorkel. A homogenization of the characteristic flow profile takes place. This process brings about a more intensive mixing in the inlet snorkel.

Twisted guide shapes of refractory material are installed between the delivery locations of the inert gas (gas injection pipes). The quantity of guide shapes is determined by the quantity of gas injection pipes.

The guide shapes having a thickness D, depth T, radius R, and are twisted at an angle α from bottom to top, i.e., in direction of the longitudinal axis of the snorkel. This angle is preferably on the order of 20° to 45°.

Accordingly, a spiral-shaped motion is imposed on the gas bubbles rising between the guide shapes which, considered over a large area, leads to a homogenization of the radial flow profile.

Due to the induced whirling, the gas bubbles no longer rise only in the vicinity of the wall, but also to a greater extent in the center of the inlet snorkel.

As a result, the previously experienced elevation of the melt above the inlet snorkel in the RH vessel is reduced. The potential energy saved in this way translates to kinetic energy. As a result, the treatment time and circulating time of the melt can be reduced. Beyond this, a reduction in the overall height of the RH vessels can be expected.

Accordingly, an advantage of one embodiment of the invention consists in that the treatment time and circulating time in the RH installation can be reduced as a result of the improved homogenization of the multiphase mixture of melt and gas bubbles. Larger quantities of gas could be used so that the kinetics of the metallurgy can be improved. Consequently, the productivity of the RH installation is increased.

BRIEF DESCRIPTION OF DRAWINGS

The invention will be described more fully in the following with reference to the drawings. In the drawings:

FIG. 1 is a perspective view of a portion of the inlet snorkel provided with guide shapes; and

FIG. 2 is a corresponding end view of an inlet snorkel.

DETAILED DESCRIPTION OF THE DRAWINGS

As can be seen, the guide shapes having a thickness D, a depth T, a radius R, and are twisted in longitudinal direction of the snorkel, namely, by an angle α.

An inlet snorkel 10 for a degassing vessel for metallurgical melting uses the RH process and includes gas injection pipes through which inert gas can be introduced into the inlet snorkel 10. The gas injection pipes are distributed along the axial length of the inlet snorkel 10. Groove-like guide shapes 12 are provided upstream of these gas injection pipes so as to project into the clear cross section of the inlet snorkel 10. In one embodiment of the invention, the guide shapes 12 are made of refractory material. The guide shapes 12 having a thickness D, a depth T, a radius R, and are twisted at an angle α in direction of the longitudinal axis of the snorkel. The angle α is preferably between 20° and 45°.

Thus, while there have shown and described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in the form and details of the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto. 

1.-4. (canceled)
 5. An inlet snorkel for a degassing vessel for metallurgical melting using an RH process, comprising: a plurality of gas injection pipes distributed along an axial length of the inlet snorkel and configured to introduce inert gas into the inlet snorkel; and a plurality of groove-like guide shapes arranged upstream of the plural gas injection pipes so as to project into an open cross section of the inlet snorkel.
 6. The inlet snorkel according to claim 5, wherein the plural groove-like guide shapes are each a refractory material.
 7. The inlet snorkel according to claim 6, wherein each of the plural groove-like guide shapes has a thickness D, a depth T, a radius R, and are twisted at an angle α in a direction of a longitudinal axis of the snorkel.
 8. The inlet snorkel according to claim 7, wherein the angle α is between 20° and 45°.
 9. The inlet snorkel according to claim 5, wherein each of the plural groove-like guide shapes has a thickness D, a depth T, a radius R, and are twisted at an angle α in a direction of a longitudinal axis of the snorkel.
 10. The inlet snorkel according to claim 7, wherein the angle α is between 20° and 45°.
 11. A method of providing flow in an inlet snorkel for a degassing vessel for metallurgical melting using an RH process comprising: introducing inert gas into the inlet snorkel via gas injection distributed along an axial length of the inlet snorkel; delivering the inert gas to a plurality of groove-like guide shapes pipes that project into an open cross section of the inlet snorkel upstream of the gas injection, whereby a passive flow guidance is provided; homogenizing a melt rising in the inlet and emulsified inert gas bubbles by the passive flow guidance by an induced swirling in the rising mixture of the melt and the emulsified insert gas bubbles; and transporting the emulsified insert gas bubbles away from a refractory wall in a direction of an axis of the inlet snorkel, wherein each of the plural guide shapes having a thickness D, depth T, a radius R, and are twisted at an angle α from bottom to top in a direction of a longitudinal axis of the snorkel, and the gas bubbles rise in a vicinity of a wall of the inlet snorkel and to a greater extent in a center of the inlet snorkel.
 12. The inlet snorkel according to claim 11, wherein the angle α is between 20° and
 45. 